Respiration (Edexcel IGCSE Biology)

Glucose is the primary source of energy in cellular respiration.

False.

ATP is produced during both aerobic respiration and anaerobic respiration, however, less ATP is produced in anaerobic respiration.

The word equation for aerobic respiration is:

glucose + oxygen → carbon dioxide + water

The balanced chemical equation for aerobic respiration is:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

False.

In the balanced chemical equation for aerobic respiration, one molecule of glucose combines with six molecules of oxygen.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

The reactants in aerobic respiration are glucose and oxygen.

The products of aerobic respiration are carbon dioxide and water.

(Products can be given in any order)

The mitochondria are the site of aerobic respiration.

Anaerobic respiration is the chemical reaction in cells that breaks down nutrient molecules to release energy without using oxygen.

False.

Anaerobic respiration does not require oxygen.

Anaerobic respiration mainly occurs in muscle cells during vigorous exercise.

Lactic acid is created during anaerobic respiration in animals.

The word equation for anaerobic respiration in animals is:

glucose → lactic acid

Glucose (C₆H₁₂O₆) should be included in the chemical equation for anaerobic respiration in animals:

C₆H₁₂O₆ → 2C₃H₆O₃

The oxygen debt is the oxygen required to remove the build up of lactic acid in muscle cells after anaerobic respiration.

Fermentation is anaerobic respiration in yeast cells, producing ethanol and carbon dioxide.

The word equation for anaerobic respiration in plants and fungi is:

glucose → alcohol + carbon dioxide

Carbon dioxide (CO₂) should be included in the equation for anaerobic respiration in plants and yeast:

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Yeast respires anaerobically to produce carbon dioxide and ethanol.

The reactants in aerobic respiration include oxygen, while the reactants in anaerobic respiration do not include oxygen.

True.

Aerobic respiration produces more ATP than anaerobic respiration.

Aerobic respiration is the process of releasing energy from glucose in the presence of oxygen.

Anaerobic respiration is the process of releasing energy from glucose in the absence of oxygen.

The waste product of anaerobic respiration in animals is lactic acid.

False.

Anaerobic respiration occurs in the absence of oxygen.

Glucose is the source of energy for both aerobic and anaerobic respiration.

False.

Anaerobic respiration involves the incomplete breakdown of glucose into lactic acid which is later broken down further as oxygen becomes available.

The purpose is to demonstrate the production of carbon dioxide and heat energy during respiration using different organisms.

The apparatus required for the investigation of carbon dioxide production in seeds include:

• Boiling tubes

• Rubber bungs

• Hydrogen carbonate indicator solution

• Cotton wool

• Glass beads

• Germinating seeds

• Boiled/dead seeds

Hydrogen carbonate indicator detects changes in carbon dioxide levels by changing colour.

Yellow indicates high carbon dioxide levels in the hydrogen carbonate indicator.

This is part of the CORMMS criteria for measuring the dependent variable.

Hydrogen carbonate indicator would remain orange because dead or boiled seeds would not be respiring so no carbon dioxide would be produced.

Living/germinating seeds or other living organisms are respiring and releasing heat energy that would be detected by a thermometer.

The independent variable when investigating respiration in seeds or other living organisms is to change whether the seeds are living or dead.

This is part of the CORMMS criteria for planning a practical.

The control variables required when investigating respiration and the production of heat include:

• Number and type of seeds

• The starting temperature of the flasks

• Material and size of the flasks

This is part of the CORMMS criteria for planning an investigation.

In a control tube containing glass beads instead of seeds when investigating respiration there would be no colour change in hydrogen carbonate indicator, it will remain orange. This is because there is no change in carbon dioxide levels in the tube.

When investigating temperature changes of respiring seeds a vacuum flask is used to contain the seeds during the experiment because it is insulated. This means that heat energy does not escape the apparatus.